github.com/nicocha30/gvisor-ligolo@v0.0.0-20230726075806-989fa2c0a413/pkg/sentry/fsimpl/gofer/handle.go (about)

     1  // Copyright 2019 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package gofer
    16  
    17  import (
    18  	"golang.org/x/sys/unix"
    19  	"github.com/nicocha30/gvisor-ligolo/pkg/context"
    20  	"github.com/nicocha30/gvisor-ligolo/pkg/lisafs"
    21  	"github.com/nicocha30/gvisor-ligolo/pkg/safemem"
    22  	"github.com/nicocha30/gvisor-ligolo/pkg/sentry/hostfd"
    23  	"github.com/nicocha30/gvisor-ligolo/pkg/sync"
    24  )
    25  
    26  var noHandle = handle{
    27  	fdLisa: lisafs.ClientFD{}, // zero value is fine.
    28  	fd:     -1,
    29  }
    30  
    31  // handle represents a remote "open file descriptor", consisting of an opened
    32  // lisafs FD and optionally a host file descriptor.
    33  //
    34  // These are explicitly not savable.
    35  type handle struct {
    36  	fdLisa lisafs.ClientFD
    37  	fd     int32 // -1 if unavailable
    38  }
    39  
    40  func (h *handle) close(ctx context.Context) {
    41  	if h.fdLisa.Ok() {
    42  		h.fdLisa.Close(ctx, true /* flush */)
    43  	}
    44  	if h.fd >= 0 {
    45  		unix.Close(int(h.fd))
    46  		h.fd = -1
    47  	}
    48  }
    49  
    50  func (h *handle) readToBlocksAt(ctx context.Context, dsts safemem.BlockSeq, offset uint64) (uint64, error) {
    51  	if dsts.IsEmpty() {
    52  		return 0, nil
    53  	}
    54  	if h.fd >= 0 {
    55  		ctx.UninterruptibleSleepStart(false)
    56  		n, err := hostfd.Preadv2(h.fd, dsts, int64(offset), 0 /* flags */)
    57  		ctx.UninterruptibleSleepFinish(false)
    58  		return n, err
    59  	}
    60  	rw := getHandleReadWriter(ctx, h, int64(offset))
    61  	defer putHandleReadWriter(rw)
    62  	return safemem.FromIOReader{rw}.ReadToBlocks(dsts)
    63  }
    64  
    65  func (h *handle) writeFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error) {
    66  	if srcs.IsEmpty() {
    67  		return 0, nil
    68  	}
    69  	if h.fd >= 0 {
    70  		ctx.UninterruptibleSleepStart(false)
    71  		n, err := hostfd.Pwritev2(h.fd, srcs, int64(offset), 0 /* flags */)
    72  		ctx.UninterruptibleSleepFinish(false)
    73  		return n, err
    74  	}
    75  	rw := getHandleReadWriter(ctx, h, int64(offset))
    76  	defer putHandleReadWriter(rw)
    77  	return safemem.FromIOWriter{rw}.WriteFromBlocks(srcs)
    78  }
    79  
    80  func (h *handle) allocate(ctx context.Context, mode, offset, length uint64) error {
    81  	if h.fdLisa.Ok() {
    82  		return h.fdLisa.Allocate(ctx, mode, offset, length)
    83  	}
    84  	if h.fd >= 0 {
    85  		return unix.Fallocate(int(h.fd), uint32(mode), int64(offset), int64(length))
    86  	}
    87  	return nil
    88  }
    89  
    90  func (h *handle) sync(ctx context.Context) error {
    91  	// If we have a host FD, fsyncing it is likely to be faster than an fsync
    92  	// RPC.
    93  	if h.fd >= 0 {
    94  		ctx.UninterruptibleSleepStart(false)
    95  		err := unix.Fsync(int(h.fd))
    96  		ctx.UninterruptibleSleepFinish(false)
    97  		return err
    98  	}
    99  	if h.fdLisa.Ok() {
   100  		return h.fdLisa.Sync(ctx)
   101  	}
   102  	return nil
   103  }
   104  
   105  type handleReadWriter struct {
   106  	ctx context.Context
   107  	h   *handle
   108  	off uint64
   109  }
   110  
   111  var handleReadWriterPool = sync.Pool{
   112  	New: func() any {
   113  		return &handleReadWriter{}
   114  	},
   115  }
   116  
   117  func getHandleReadWriter(ctx context.Context, h *handle, offset int64) *handleReadWriter {
   118  	rw := handleReadWriterPool.Get().(*handleReadWriter)
   119  	rw.ctx = ctx
   120  	rw.h = h
   121  	rw.off = uint64(offset)
   122  	return rw
   123  }
   124  
   125  func putHandleReadWriter(rw *handleReadWriter) {
   126  	rw.ctx = nil
   127  	rw.h = nil
   128  	handleReadWriterPool.Put(rw)
   129  }
   130  
   131  // Read implements io.Reader.Read.
   132  func (rw *handleReadWriter) Read(dst []byte) (int, error) {
   133  	n, err := rw.h.fdLisa.Read(rw.ctx, dst, rw.off)
   134  	rw.off += n
   135  	return int(n), err
   136  }
   137  
   138  // Write implements io.Writer.Write.
   139  func (rw *handleReadWriter) Write(src []byte) (int, error) {
   140  	n, err := rw.h.fdLisa.Write(rw.ctx, src, rw.off)
   141  	rw.off += n
   142  	return int(n), err
   143  }
   144  
   145  // ReadToBlocks implements safemem.Reader.ReadToBlocks.
   146  func (rw *handleReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
   147  	n, err := rw.h.readToBlocksAt(rw.ctx, dsts, rw.off)
   148  	rw.off += n
   149  	return n, err
   150  }
   151  
   152  // WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
   153  func (rw *handleReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
   154  	n, err := rw.h.writeFromBlocksAt(rw.ctx, srcs, rw.off)
   155  	rw.off += n
   156  	return n, err
   157  }